U.S. patent application number 09/805168 was filed with the patent office on 2001-09-27 for fuel injection system for internal combustion engine.
Invention is credited to Kadomukai, Yuzo, Miyajima, Ayumu, Nagano, Masami, Okamoto, Yoshio, Someno, Tadashi.
Application Number | 20010023686 09/805168 |
Document ID | / |
Family ID | 18595274 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010023686 |
Kind Code |
A1 |
Okamoto, Yoshio ; et
al. |
September 27, 2001 |
Fuel injection system for internal combustion engine
Abstract
In a port fuel injection lean burn engine, attaching of fuel
spray onto a wall surface, which is a problem at atomizing injected
fuel, is reduced, and the quality and shaping state of the mixed
gas in cylinders of the engine is improved. The engine comprises a
fuel injector 1; an intake valve 6 for opening and closing an
intake port; and an intake air flow control device 10. The injected
fuel is shaped in a low penetration fuel spray when the engine is
operated in a low load and low rotation speed, and the injected
fuel is shaped in a high penetration fuel spray when the engine is
operated in a high load and high rotation speed. The fuel is
injected in synchronism with the intake stroke of the engine, and
is transported by the air flow flowing through the intake air flow
control device 10 to suppress attaching of fuel spray onto a wall
surface.
Inventors: |
Okamoto, Yoshio; (Minori,
JP) ; Kadomukai, Yuzo; (Ishioka, JP) ;
Miyajima, Ayumu; (Narita, JP) ; Nagano, Masami;
(Hitachinaka, JP) ; Someno, Tadashi; (Hitachinaka,
JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
18595274 |
Appl. No.: |
09/805168 |
Filed: |
March 14, 2001 |
Current U.S.
Class: |
123/490 ;
361/152 |
Current CPC
Class: |
F02B 31/06 20130101;
F02D 2041/2034 20130101; F02D 41/20 20130101; Y02T 10/12 20130101;
F02D 2041/2051 20130101 |
Class at
Publication: |
123/490 ;
361/152 |
International
Class: |
H01H 047/00; H01H
047/28; H01H 047/32; F02M 051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2000 |
JP |
2000-77774 |
Claims
What is claimed is:
1. A fuel injection system for an internal combustion engine
comprising a fuel injector for injecting fuel, said fuel injector
having a fuel passage adding a swirl force to the fuel, said fuel
injector being opened by driving a valve body toward a direction
apart from a valve seat; and a controller for controlling driving
of said valve body, wherein said controller controls driving of
said valve body so that a rising speed of said valve body at valve
opening may be slower when the internal combustion engine is
operated in a high load and high rotation speed state than when the
internal combustion engine is operated in a low load and low
rotation speed state.
2. A fuel injection system for an internal combustion engine
comprising a fuel injector for injecting fuel, said fuel injector
having a fuel passage adding a swirl force to the fuel, said fuel
injector being opened by driving a valve body toward a direction
apart from a valve seat; and a controller for controlling driving
of said valve body, wherein said controller controls driving of
said valve body so that a time required until said valve body is
moved from a closed state by a preset stroke to be opened may be
longer when the internal combustion engine is operated in a high
load and high rotation speed state than when the internal
combustion engine is operated in a low load and low rotation speed
state.
3. A fuel injection system for an internal combustion engine
according to any one of claims 1 and 2, wherein said fuel injector
is an electromagnetic valve which drives the valve body by
switching voltage applied to a coil among a plurality of voltage
values to vary an electromagnetic force, and said controller
controls a voltage applying time period from a time point of
switching the voltage from a first voltage value to a second
voltage value in order to drive said valve body toward the valve
opening direction to a time point of again switching the voltage
applied to the coil to said first voltage value while said valve
body is being moved from a closed state by a preset stroke to be
opened so that the voltage applying time period in the following
time may be longer than the voltage applying time period in the
preceding time when the internal combustion engine is operated in a
high load and high rotation speed state, and so that the voltage
applying time period in the following time may be shorter than the
voltage applying time period in the preceding time when the
internal combustion engine is operated in a low load and low
rotation speed state.
4. A fuel injection system for an internal combustion engine
according to any one of claims 1 and 2, wherein said fuel injector
is an electromagnetic valve which drives the valve body by
switching voltage applied to a coil among a plurality of voltage
values to vary an electromagnetic force, and said controller
controls a voltage applying time period from a time point of
switching the voltage from a first voltage value to a second high
voltage value in order to drive said valve body toward the valve
opening direction to a time point of again switching the voltage
applied to the coil to said first voltage value so that the voltage
applying time period in the first time may be shorter when the
internal combustion engine is operated in a high load and high
rotation speed state than when the internal combustion engine is
operated in a low load and low rotation speed state.
5. A fuel injection system for an internal combustion engine
according to any one of claims 1 and 2, wherein said fuel injector
is an electromagnetic valve which drives the valve body by
switching voltage applied to a coil among a plurality of voltage
values to vary an electromagnetic force, and said controller
controls a magnitude of voltage varied in order to drive said valve
body toward the valve opening direction while said valve body is
being moved from a closed state by a preset stroke so that the
magnitude of the varied voltage in the following time may be larger
than the magnitude of the varied voltage in the preceding time when
the internal combustion engine is operated in a high load and high
rotation speed state, and so that the magnitude of the varied
voltage in the following time may be smaller than the magnitude of
the varied voltage in the preceding time when the internal
combustion engine is operated in a low load and low rotation speed
state.
6. A fuel injection system for an internal combustion engine
according to any one of claims 1 and 2, wherein said fuel injector
is an electromagnetic valve which drives the valve body by
switching voltage applied to a coil among a plurality of voltage
values to vary an electromagnetic force, and said controller
controls a magnitude of voltage varied in order to drive said valve
body toward the valve opening direction so that the magnitude of
the varied voltage in the first time may be smaller when the
internal combustion engine is operated in a high load and high
rotation speed state than when the internal combustion engine is
operated in a low load and low rotation speed state.
7. A fuel injection system for an internal combustion engine
injecting fuel inside an air intake passage for conveying air into
a cylinder of said internal combustion engine, said fuel injection
system injecting the fuel by varying a penetration force of the
fuel corresponding to an operating state of said internal
combustion engine, which comprises: a movable member arranged
inside said intake air passage in an upstream side of a position
where fuel spray is injected, said movable member being driven so
that an area of said movable member projected on the cross section
of said intake air passage may be varied; and a controller
controlling said area of said movable member projected on the cross
section of said intake air passage so as to be smaller when the
internal combustion engine is operated in a high load and high
rotation speed state than when the internal combustion engine is
operated in a low load and low rotation speed state.
8. A fuel injection system for an internal combustion engine
injecting fuel inside an air intake passage for conveying air into
a cylinder of said internal combustion engine, said fuel injection
system injecting the fuel by varying a penetration force of the
fuel corresponding to an operating state of said internal
combustion engine, which comprises: an opening-and-closing device
arranged inside said intake air passage in an upstream side of a
position where fuel spray is injected, said opening-and-closing
device opening and closing part of a cross-sectional area of said
intake air passage; and a controller controlling said
opening-and-closing device so that may be smaller when the internal
combustion engine is operated in a high load and high rotation
speed state than when the internal combustion engine is operated in
a low load and low rotation speed state.
9. A fuel injection system for an internal combustion engine
injecting fuel inside an air intake passage for conveying air into
a cylinder of said internal combustion engine, said fuel injection
system injecting the fuel by varying a penetration force of the
fuel corresponding to an operating state of said internal
combustion engine, wherein one selected from a particle size of the
fuel and said penetration force of the fuel is varied in accordance
with at a low speed and at a high speed of the internal combustion
engine.
10. A fuel injection system for an internal combustion engine
according to claim 9, wherein said one selected from a particle
size of the fuel and said penetration force of the fuel is varied
in accordance with at a fuel pressure of the fuel.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a fuel injection system for
an internal combustion engine, and particularly to a technology for
controlling fuel to attach onto a wall surface of an intake
manifold by controlling penetration of fuel spray (fuel spray
travel).
[0003] 2. Prior Art
[0004] As a known conventional fuel injection system, a system is
disclosed in Japanese Patent Application Laid-Open No.5-126012. In
this publication, it is described that since rotation speed of an
engine is low and closing time of the intake valve is long when the
engine is operated in a low speed range such as at starting
operation or at idling operation, the fuel spray from the fuel
injector of electromagnetic type is preferably suspended inside the
intake manifold, and the penetration force of the fuel spray is
preferably weak and the fuel becomes fine liquid droplets.
[0005] It is also described that on the other hand, since rotation
speed of the engine is high and closing time of the intake valve is
short as the rotation speed of the engine is brought from a middle
speed range to a high speed range, the fuel spray must be rapidly
supplied to the combustion chamber without being attached onto the
inner wall surface of the intake manifold, and accordingly the
penetration force of the spray needs to be strong.
[0006] In the system described in the publication, the electronic
control fuel injection system for internal combustion engine of a
multi-point injection type has an electromagnetic fuel injector for
injecting fuel toward a dish portion of the intake valve for each
cylinder, wherein the shape of fuel spray is varied depending on an
operating condition of the engine by detecting the operating
condition of the engine, and by driving a fuel spray shape varying
means of the electromagnetic fuel injector using the detected
signal.
[0007] The system varies the fuel spray shape by controlling a
ratio of a swirl fuel component to a non-swirl fuel component. The
swirl force of the swirl fuel component is added when the fuel
passes through a fuel passage (groove) for introducing the fuel
eccentrically to an axis, the fuel passage being formed in a fuel
swirling element.
[0008] On the other hand, the non-swirl component is fuel passing
through a gap between an inner peripheral surface of the fuel
swirling element and a ball composing the valve body. For example,
when the size of the gap is increased, an amount of fuel leaking
through the gap is increased to increase the non-swirl component,
and the shape of the fuel spray becomes a shape having a small
injection angle which is suitable for high speed operation of the
engine.
[0009] In the system described above, a piezoelectric element is
used in order to vary the size of the gap between the inner
peripheral surface of the fuel swirling element and the ball
composing the valve body. Therefore, the fuel spray shape varying
means using the piezoelectric element needs to be formed in a very
narrow space of a nozzle end portion of the fuel injector, which
causes a problem of improving the productivity.
[0010] Further, it is necessary to take the wiring to the
piezoelectric element into consideration. In addition, the problem
of reliability such as change in characteristic and durability of
the piezoelectric element should be considered.
[0011] In the above-mentioned publication, no consideration is paid
on a system for injecting fuel so as to meet the timing of fuel
injection with the timing of intake stroke. A lean burn engine is
an engine in which a lean mixed gas is burned, and the mixed gas is
made lean by employing a fuel injection method of injecting fuel
from a fuel injector provided in each cylinder (multi-point
injection system: MPI) and by performing fuel injection in
synchronism with intake stroke.
[0012] In a fuel injection system required to perform fuel
injection in synchronism with intake stroke used, for example, in
the such an engine described above, a time lag (transport lag)
until the injected fuel spray reaches the inside of the cylinder
becomes a problem. In a case where the penetration force of fuel
spray is varied, the time until the fuel spray reaches to the
inside of the cylinder is different between a fuel spray having a
high penetration and a fuel spray having a low penetration.
Therefore, it is necessary to take the transport lag of the fuel
spray into consideration.
SUMMARY OF THE INVENTION
[0013] A first object of the present invention is to make the
penetration of fuel spray controllable without large modification
of the fuel injector. A second object of the present invention is
to reduce the transport lag of the fuel spray even when the
penetration of fuel spray is varied.
[0014] In order to attain the above first object, a swirl velocity
component and an axial velocity component of fuel are varied by
controlling a rising speed of a valve body of the fuel injector. In
detail, by increasing a speed of opening the valve to rapidly
increase a swirl force of fuel, the swirl velocity component of the
fuel is strengthened and the axial velocity component is weakened.
By doing so, a fuel spray having a small penetration force (a low
penetration fuel spray) can be obtained.
[0015] On the other hand, by decreasing the speed of opening the
valve and then gradually increasing a swirl force of fuel, at the
initial stage of the fuel injection, the swirl velocity component
of the fuel is weakened and the axial velocity component is
strengthened. By doing so, a fuel spray having a large penetration
force (a high penetration fuel spray) can be obtained. Because the
method does not need modification of the structure nor does not
cause complexity in the constitution of internal parts, the method
described above has advantages of very low cost and improvement in
the reliability compared to the method of mechanical operation.
[0016] In order to attain the above second object, an intake air
velocity is changed corresponding to the high penetration fuel
spray or the low penetration fuel spray by varying a
cross-sectional area of an intake passage in an upstream side of
the fuel injector. In detail, in a case of the low penetration fuel
spray in which the fuel spray can reach only at a position upstream
of the intake valve, the transport lag of the fuel spray is reduced
by increasing the velocity of the intake air flow velocity.
Increasing of the velocity of the intake air flow velocity may be
performed by decreasing the cross-sectional area of the intake air
passage.
[0017] In that case, the intake air flow in a bending passage of
the intake manifold is guided in a passage wall side opposite to a
position of the intake manifold where the fuel injector is
arranged. Thereby, it is possible to prevent the fuel spray from
attaching onto the passage wall in the opposite side of the
position of the intake manifold where the fuel injector is
arranged, or to reduce an amount of fuel spray attaching onto the
passage wall.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is partially cross-sectional views showing a cylinder
of a multi-cylinder internal combustion engine mounting a fuel
injector of the present embodiment, and FIG. 1 (a) shows flow of
fuel spray and intake air in a case where an operating state of the
engine is in a low load and low rotation speed state, and FIG. (b)
shows flow of fuel spray and intake air in a case where an
operating state of the engine is in a high load and high rotation
speed state;
[0019] FIG. 2 is a diagram showing the total construction of an
embodiment of a control system of an engine mounting an embodiment
of a fuel injector in accordance with the present invention;
[0020] FIG. 3 (a) is a cross-sectional view showing the fuel
injector of FIG. 1, and FIG. 3 (b) is a cross-sectional view
showing the fuel injector being taken on the plane of the line I-I
of FIG. 3 (a);
[0021] FIG. 4 is a block diagram showing the construction of an
embodiment of a fuel injection system in accordance with the
present invention;
[0022] FIG. 5 (a) is charts showing a waveform of the valve
behavior in a case where an operating state of the engine is in a
low load and low rotation speed state, and FIG. 5 (b) is charts
showing a waveform of the valve behavior in a case where an
operating state of the engine is in a high load and high rotation
speed state; and
[0023] FIG. 6 (a) is charts showing another embodiment of a
waveform of the valve behavior in a case where an operating state
of the engine is in a low load and low rotation speed state, and
FIG. 6 (b) is charts showing another embodiment of a waveform of
the valve behavior in a case where an operating state of the engine
is in a high load and high rotation speed state.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0024] An embodiment of a fuel injection system for an internal
combustion engine in accordance with the present invention will be
described below in detail, referring to the accompanied
drawings.
[0025] Initially, the whole construction of the engine control
system comprising the embodiment of the fuel injection system (the
fuel injector 1) in accordance with the present invention will be
described, referring to FIG. 2.
[0026] In each of cylinders 9 of an internal combustion engine 100
composed of four cylinders (only one of the four cylinders is
illustrated in the figure), a combustion chamber is formed by
arranging an ignition plug 12, and an intake valve 6 and an exhaust
valve 7, and a piston 8 reciprocally moving in the cylinder 9. In
this embodiment, the engine is of a 4-cylinder engine, but number
of the cylinders is not limited to four. In each of the cylinders
9, an intake manifold 18 and an exhaust manifold 19 opened and
closed by the intake valve 6 and the exhaust valve 7 respectively
are arranged. In the intake manifold 18, an intake air flow sensor
2 for measuring a mass flow rate of intake air, which is one of
operating state detecting means; and a throttle sensor 4 for
measuring an opening degree of a throttle valve 3 are appropriately
arranged.
[0027] Further, a cooling water sensor 14 for measuring cooling
water of the engine; and a crank angle sensor 13 for measuring a
rotation speed of the engine are appropriately arranged. Air
flowing through an air cleaner 20 provided in an upstream of the
intake manifold 18 is controlled its flow rate by the throttle
valve 3, and is mixed with gasoline injected in an appropriate fuel
spray characteristic from each of the fuel injectors 1 of the fuel
injection system to be supplied to each of the cylinders 9. The
fuel injectors 1 are individually arranged in the upstream of the
cylinders 9 of the 4-cylinder internal combustion engine 100 to
form the fuel injection method of multi-point injection (MPI)
system.
[0028] On the other hand, fuel from a fuel tank 21 is pumped up and
pressurized by a fuel pump 22, and then conducted to a fuel inlet
of the fuel injector 1 through a fuel pipe 23 having a pressure
regulator 15. The fuel conducted to the fuel injector 1 is
controlled to a constant fuel pressure by a fuel pressure regulator
16, and the extra fuel is returned to the fuel tank 21.
[0029] Exhaust gas burned in each of the cylinders 9 is conducted
to a catalyst converter (not shown) through an exhaust manifold 19
to be cleaned, and then exhausted. In the exhaust manifold 19,
there is arranged an air-fuel ratio sensor 17 for output a
wide-ranged and linear air-fuel ratio signal in proportion to an
oxygen concentration in the exhaust gas.
[0030] An output signal 2s indicating an amount of intake air
obtained from the intake air flow sensor 2, an output signal 4s
from the throttle sensor 4, and signals 14s, 13s and 17s from the
cooling water sensor 14, the crank angle sensor 13 and the air-fuel
ratio sensor 17 are input to an engine control unit (control unit
C/U) 11 as electric signals indicating an operating state of the
internal combustion engine 100.
[0031] The control unit 11 is arranged in a vehicle body or an
engine room, and executes necessary calculation processing based on
the electric signals indicating the operating state of the internal
combustion engine 100 from the various kinds of sensors, and
outputs signals for performing to open and close the fuel injector
1 for injecting and supplying fuel, to drive the ignition plug 12,
and to open and close an idle speed control valve (ISC) 5 for
controlling so that a rotation speed of the engine at idling
operation may become a target rotation speed in order to perform
the optimum control for the operating state, and at the same time
controls the fuel pump 22 and a swirl control valve drive unit
10.
[0032] Further, the control unit 11 outputs a command signal to
perform fuel injection to each of the cylinders 9 so as to
synchronize the timing of fuel injection with an intake stroke of
each of the cylinders 9. The control unit 11 is composed of an I/O
as an input/output interface, a calculation processor unit MPU,
memory units RAM and ROM storing many control programs, a timer
counter and so on.
[0033] In the control unit 11, a fuel injection amount setting
means, which is formed by executing calculation based on a control
program by the calculation processing unit MPU, calculates a
required fuel amount to be supplied to the cylinder 9 from the fuel
injector 1 based on the detected intake air flow rate and a set
air-fuel ratio, and calculates a required injection pulse width (a
valve opening time period of the fuel injector 1) based on the
required fuel amount, a flow rate gradient and an ineffective
injection pulse width of the injection amount characteristic of the
fuel injector 1 to output a drive signal is so that the fuel
injector 1 may perform valve opening for the time period of the
injection pulse based on the required injection pulse width.
[0034] Further, the fuel injection amount setting means formed by
executing calculation based on a control program by the calculation
processing unit MPU calculates an injection timing of the fuel
injector 1 based on the intake air amount and an engine rotation
speed and so on to synchronize with the intake stroke of the
internal combustion engine 100, and at the same time sets the fuel
injection timing during the intake stroke to the optimum timing.
Based on the timing, the fuel injection amount setting means
outputs drive signals 1s, 12s, 10s to the fuel injector 1, the
ignition plug 12 and the swirl control valve drive unit 10,
respectively.
[0035] The swirl control valve drive unit 10 is a unit for opening
and closing a swirl control valve (SCV) 10a which is an air flow
speed accelerating means for generating a tumble flow (tumble
swirl), and is arranged in the upstream of the fuel injector 1. The
SCV 10a makes the flow passage area (cross-sectional area of the
flow passage) of the intake manifold 18 narrow by being driven
toward the closed direction to increase the velocity of air by the
tumble swirl.
[0036] As described above, the SCV 10a is a movable member for
varying the area projected on the flow passage of the intake
manifold to form an opening-and-closing device for opening and
closing part of the flow passage.
[0037] Therein, the meaning that the optimum mixed gas is formed by
the MPI system to improve the combustion in the internal combustion
engine 100 having the fuel injector 1 is that attaching of the
injected fuel onto the wall surface is suppressed to solve the time
lag of the fuel reaching to the cylinder 9 and to improve the
quality and shaping state of the mixed gas inside the cylinder
9.
[0038] The time lag of the fuel reaching to the cylinder 9 is
composed of a transport lag of the injected fuel from the time
point when the fuel is injected from the fuel injector 1 to the
time point when the fuel is actually taken in the cylinder 9; and a
calculation lag and a process lag from the time point when the
required injection amount is calculated from the intake air flow
rate detected from the intake air flow sensor 2 and so on to the
timing when the fuel is injected from the fuel injector 1.
[0039] In order to solve the time lag of the injected fuel, it is
necessary that the fuel injector 1 injects the fuel in synchronism
with the intake stroke of the cylinder 9 based on new data of the
intake air flow sensor 2 and that all the fuel injected by the fuel
injector 1 is taken in the cylinder 9 in the intake stroke.
[0040] Therefore, in order to attain the above time lag problem,
the injection of fuel by the fuel injector 1 must be completed at
an appropriate timing of the intake stroke of the cylinder 9. That
is, it means that all the fuel injected through the fuel injector 1
has been taken into the cylinder 9 during the short time period
from opening to closing of the intake valve 6. In that case, taking
the fuel injection time period (the injection pulse width) into
consideration, it is necessary to prevent the injected fuel from
attaching onto the inner wall surface of the intake manifold
18.
[0041] Further, the quality and shaping state of the mixed gas
inside the cylinder 9 means that the mixed gas is formed in a lean
state, and only a flammable and dense mixed gas is gathered around
the ignition plug. One of effective means to improve the quality
and shaping state of the mixed gas is to develop atomizing the
injected fuel. Since kinetic energy of the atomized injected fuel
is smaller than that of spray fuel having a normal droplet size,
the atomized injected fuel takes a longer time to travel to the
cylinder 9.
[0042] Therefore, in order to avoid the longer time travel, by the
synergistic effect of a kinetic energy control means for the
atomized fuel (a means for controlling penetration of the fuel
spray) and a fuel injection timing setting means, an injection
timing for shaping a further optimum mixed gas state is set within
the fuel injection timing during the intake stroke so that only a
flammable and dense mixed gas may be gathered around the ignition
plug 12 to improve the quality of the mixed gas.
[0043] FIG. 1 is partially cross-sectional views showing the fuel
injector 1 mounted on a multi-cylinder internal combustion engine,
and shows shapes of the mixed gas which can be formed in the
present embodiment.
[0044] The intake manifold has a bent passage in the upstream side
of the valve seat of the intake valve, and the shaft of the intake
valve is inserted from the passage wall in the outer side of the
bent passage. The fuel injector 1 is arranged in the upstream side
of the position where the shaft of the intake valve is inserted so
that the fuel spray may be injected into the intake manifold from
the passage wall in the outer side.
[0045] The swirl control valve 10a is arranged in the further
upstream side of the position where the fuel spray is injected into
the intake manifold from the fuel injector, and is disposed so as
to open and close the passage cross section from the center of the
intake manifold to the side where the fuel injector is disposed.
That is, about a half of the total cross-sectional area of the
passage can be opened and closed.
[0046] FIG. 1 (a) shows intake air flow in the intake manifold 18
and a formed shape of fuel spray from the fuel injector 1 (in a
state that the kinetic energy of the fuel spray is small, that is,
in a state of a low penetration fuel spray having a small
penetrating force) in a case where an operating state of the
internal combustion engine 100 is in a low load and low rotation
speed state.
[0047] On the other hand, FIG. 1 (b) shows intake air flow in the
intake manifold 18 and a formed shape of fuel spray from the fuel
injector 1 (in a state that the kinetic energy of the fuel spray is
large, that is, in a state of a high penetration fuel spray having
a large penetrating force) in a case where an operating state of
the internal combustion engine 100 is in a high load and high
rotation speed state.
[0048] The reference character 110 indicates one of the cylinders 9
of the multi-cylinder internal combustion engine, the reference
character 6 indicates the intake valve opening and closing the
intake port 25, the reference character 6a indicates the dish
portion of the intake valve 6, the reference character 10a
indicates the swirl control valve, the reference character 18
indicates the intake manifold, the reference character 18a
indicates the intake air flow, and the reference character 26
indicates the combustion chamber.
[0049] Therein, the operating state of the internal combustion
engine 100 is obtained by necessary calculation processing based on
the electric signals output from the various kinds of sensors
arranged in the vehicle body or in the engine room. The low load
and low rotation speed state in the present embodiment means a
state within a range of an engine water temperature of 20 to
30.degree. C. and an engine rotation speed of 1000 to 2000 rpm to
an engine water temperature of 80.degree. C. and an engine rotation
speed of 600 to 900 rpm, that is, a state of what is called idle
operation within the above target engine rotation speed.
[0050] On the other hand, the high load and high rotation speed
state means a state in which the throttle valve 3 is an almost
fully opened state. In that state, pressure in the intake manifold
18 is within a range of 81 kPa to 101 kPa (atmospheric pressure).
On the other hand, during idling operation, the pressure in the
intake manifold 18 is within a range of 28 kPa to 41 kPa.
[0051] As shown in FIG. 1 (a), when the shape of the fuel spray
from the fuel injector 1 is a low penetration fuel spray having a
small penetration force in which the front end of the fuel spray is
positioned near the center of the intake manifold 18, the fuel is
transported into the combustion chamber 26 by being conveyed on the
intake air flow of which the velocity is increased in the wall side
opposite to the fuel spray. The velocity-increased intake air flow
is formed when the swirl control valve 10a closes the portion of
the passage from the center of the intake manifold to the side
where the fuel injector 1 is arranged (one-half of the total area
of the passage).
[0052] On the other hand, as shown in FIG. 1 (b), when the shape of
the fuel spray from the fuel injector 1 is a high penetration fuel
spray having a large penetration force in which the front end of
the fuel spray is formed close to the dish portion 6a of the intake
valve 6, the fuel spray penetrates through the intake air flow
flowing around the front end 1a of the fuel injector 1 to be
transported into the combustion chamber 26.
[0053] According to the construction described above, by the high
penetration fuel spray in the high load and high rotation speed
state, or by increasing the velocity of the intake air flow in the
low load and low rotation speed state, the atomized injected fuel
can be transported into the cylinder 9 without increasing the time
period of the fuel traveling to the combustion chamber 26.
Therefore, the fuel injection can be completed within the intake
stroke, and only the flammable dense mixed gas can be gathered
around the ignition plug 12.
[0054] Further, since the swirl control valve 10a closes the
portion of the passage in the arranging side of the fuel injector 1
to guide the intake air flow to the passage wall side opposite to
the arranging side of the fuel injector 1, the fuel spray having a
wide spray angle caused by the low penetration fuel spray can be
prevented from or reducing of attaching onto the passage wall in
the side opposite to the arranging side of the fuel injector 1.
[0055] Description will be made below on the structure and the
operation of the fuel injector 1 capable of forming such fuel
sprays described above, referring to FIG. 3. FIG. 3 (a) is a
cross-sectional view showing the fuel injector 1, and FIG. 3 (b) is
a cross-sectional view showing the fuel injector being taken on the
plane of the line I-I of FIG. 3 (a).
[0056] The fuel injector 1 performs injection of fuel by opening
and closing a seat portion based on an ON-OFF signal of a duty
calculated by the control unit. A magnetic circuit is composed of a
cylindrical yoke 27 with bottom, a core 28 and a plunger 29 facing
the core 28 through a gap. A rod 30 with a fuel passage 31 inside
and a valve body 32 connected to the rod 30 are joined to the
plunger 29, and the valve body 32 performs opening and closing of a
seat face formed in a nozzle member 33.
[0057] Further, a spring 34 as an elastic member pressing the valve
body 32 to the seat face is arranged in the center of the core 28,
and a spring adjuster 35 inserted through the center of the core 28
in order to adjust a set load is arranged in the upper end of the
spring 34. A coil 36 for exciting the magnetic circuit is wound
around a bobbin 37, and the outer periphery is molded with a
plastic material. A terminal 38 of the coil 36 is connected to a
terminal of the control unit, not shown.
[0058] On the other hand, guiding for smoothly moving the valve
body 32 in the axial direction is performed by a guide portion 30a
provided in the valve body 32 and an inner wall of a cylindrical
fuel swirl member 39 inserted into an inner wall of a hollow
portion of the nozzle member 33. The fuel swirl member 39 is one of
the fuel atomizing means. In the nozzle member 33, a seat face for
seating the valve body 32 is formed following to the cylindrical
fuel swirl member 39, and a fuel injection hole 42 for allowing
fuel to pass through is formed in the center of the seat face.
[0059] FIG. 3 (b) is a cross-sectional view showing the fuel swirl
member 39 of the fuel atomizing means. The fuel is introduced from
the upper side of the valve body 32 to flow to the fuel swirl
member 39. The fuel introduced from a axial passage 40 is
introduced by a radial passage 41 sufficiently eccentric to the
valve axis so as to sufficiently add swirl energy to the fuel.
Atomizing of the fuel is further developed by constructing an
annular gap formed between the valve body 32 and the seat face at
opening the valve body 32 so as to reduce hydrodynamic loss.
[0060] Further, the valve body 32 is operated in high speed by
controlling waveform of the current input to the coil 36, and the
valve body 32 is opened and closed in a short time to cause rapid
change in pressure of the injected fuel during the operation. By
such a construction, swirl energy enough to develop the atomization
is added to the fuel in the fuel injection hole 42. The fuel
injection hole 42 is designed so that the supplied energy may be
effectively discharged outside the hole. For example, the length of
the hole is shortened in order to reduce hydrodynamic loss in the
axial direction of the hole.
[0061] In a case where a atomizing method other than the method of
using swirl of the fuel, for example, a method of making the
injected fuel in a thin-film shape to develop atomization by
forming the injection hole portion in a very narrow annular gap,
the present embodiment can be used.
[0062] The operation of the fuel injector 1 will be described
below. The fuel injector 1 performs fuel injection control by
operating the valve body 32 to open and close the seat face
according to the electric ON-OFF signal supplied to the coil 36.
When the electric signal from the control unit 11 is supplied to
the coil 36, a magnetic circuit is formed by the core 28, the yoke
27 and the plunger 29 to attract the plunger 29 toward the core 28
side. As the plunger 29 is moved, the valve body 32 formed together
with the plunger in a one-piece structure is also moved to be
detached from the seat face of the valve seat of the nozzle member
33 and accordingly to open the fuel injection hole 42.
[0063] The fuel is pressurized and regulated through the fuel pump
and the regulator for adjusting the fuel pressure, and flows into
the inside of the fuel injector 1, and then is injected out of the
fuel injection hole 42 via the inner passage 31 of the valve body
30, the outer peripheral portion of the valve body 32, and the
axial direction passage 40 and the radial direction passage of the
fuel swirl member 39.
[0064] The method of controlling the penetration of the fuel spray
will be described below, referring to FIG. 4, FIG. 5 and FIG. 6.
The control of penetration of the fuel spray in the fuel injector 1
of the present embodiment is adjusted by the intensity of swirl
force (swirl force) of the fuel added to the injected fuel. In
detail, the valve opening speed up to the full stroke the valve
body 32 is controlled. That is, when the valve opening speed is
increased, the swirl force of the fuel is instantaneously increased
to strengthen the swirl velocity component of the fuel and weaken
the axial velocity component. Therefore, the penetration force of
the fuel spray is weakened to obtain the low penetration fuel
spray.
[0065] On the other hand, when the valve opening speed is
decreased, the swirl force of the fuel is gradually increased, and
accordingly the swirl velocity component is weak and the axial
velocity component is strong during the initial stage of injection.
Therefore, the penetration force of the fuel spray is strengthened
to obtain the high penetration fuel spray.
[0066] FIG. 4 is a block diagram showing the construction of the
present embodiment of the fuel injection system. In order to
control conduction of current to the coil 36, one terminal of the
coil is connected to a power transistor 54 and the other terminal
is grounded through a current detecting resistor 57 and connected
to a power transistor 56 in parallel. The base of the power
transistor 54 is connected to a current control circuit 53, and the
other is connected to a battery power source 58.
[0067] On the other hand, the base of the power transistor 56 is
connected to the current control circuit 53, but the other is
connected to the coil 36 through a diode 55. Signals from the
engine controller 11 and a current comparator 52 are input to the
current control circuit 53, but the signal from the engine
controller 11 is a command pulse signal (pulse width Ti) determined
corresponding to an operating state of the engine, and a signal
from the current comparator 52 is a compared signal between a coil
current and a target current.
[0068] The current control circuit 53 operates the power
transistors 54, 56 corresponding to an ignition command pulse, and
the power transistor 54 side performs control patterns up to a
target peak current Ip by ON-OFF operation, and after reaching the
target current value, the power transistor 56 repeat ON-OFF
operation in order to conduct a hold current smaller than the
target current value to the coil 36.
[0069] FIG. 5 shows input current waveforms and applied voltage
waveforms to the coil, and displacement waveform of the valve body
32.
[0070] FIG. 5 (a) shows a case where in order to shorten the time
period reaching the target peak current value Ip, the time width of
the applied voltage is changed from large width to small width, and
then the current is switching to the hold current value Ih to
repeating ON-OFF operation with a constant time interval. By the
control described above, the displacement of the valve is rapidly
raised up to the full stroke (valve opening time To) after a dead
time Tc.
[0071] FIG. 5 (b) shows a case where the time width of the applied
voltage is controlled to be gradually increased from a small width
to a large width so that the target peak current value may become
nearly equal to the hold current value Ih. By the control described
above, the displacement of the valve is slowly raised up to the
full stroke.
[0072] The displacement of the valve shown in FIG. 5 (a) makes the
fuel injected from the fuel injector 1 in a shape of low
penetration fuel spray. The displacement of the valve shown in FIG.
5 (b) makes the fuel injected from the fuel injector 1 in a shape
of high penetration fuel spray. In the figure, the reference
character Tb indicates a time lag of closing the valve.
[0073] FIG. 6 shows another embodiment of voltage waveform applied
to the coil 36.
[0074] FIG. 6 (a) shows a method in which in order to shorten the
time period reaching the target peak current value Ip, the applied
voltage is continuously input for a preset time period, and then
the current is switching to the hold current value Ih. This method
is a peak hold method, and the actual effective voltage of the
applied voltage is controlled so as to be equivalent to that of
FIG. 5 (a).
[0075] FIG. 6 (b) shows a method in which the applied voltage is
input stepwise so as to gradually reach the target hold current
value Ih, and the actual effective voltage of the applied voltage
is also controlled so as to be equivalent to that of FIG. 5 (b). By
the control described above, the behavior of the valve displacement
can be similar to that of the first embodiment.
[0076] In addition to the penetration control methods of the
present embodiments, various change and modification may be made in
design, for example, the swirl force of fuel can be varied by
mechanically moving the fuel swirl member 39.
[0077] Further, in order to shorten the time period reaching the
target peak current value Ip, the applied voltage to the coil may
be increased. Therefore, for example, when a high penetration fuel
spray is formed, the rise of the valve body can be made slower the
that in forming a low penetration fuel spray by decreasing the
applied voltage at the beginning of driving the valve body.
[0078] As described above, the present embodiment has the following
functions. In the fuel injector 1 of the MPI system, since the fuel
can be atomized because the fuel injector 1 uses the fuel swirl
member 39, and the penetration control of the fuel spray is
performed corresponding to the operating state of the internal
combustion engine 100, the quality and shaping state of the mixed
gas inside the cylinder 9 can be improved.
[0079] Further, the fuel injector 1 can inject a required injection
amount of fuel in a short time at an optimum position during the
intake stroke, and can form an optimum mixed gas in the combustion
chamber 26 by eliminating time lag.
[0080] Furthermore, since the internal combustion engine 100 has
the swirl control valve 10a for accelerating air flow velocity in
the intake manifold 18 and the fuel spray from the fuel injector 1
is the low penetration fuel spray to the velocity accelerated air
flow in the intake manifold 18, attaching of the injected fuel onto
the wall surface and the transport time lag due to the atomization
can be solved.
[0081] According to the present invention, since the penetration
force of the fuel spray is varied by changing the displacement
speed of the valve body, the penetration force of the fuel spray
can be controlled without large change in the structure of the fuel
injector.
[0082] Further, when the penetration force of the fuel spray is
varied, the transport time lag of the fuel spray can be reduced by
changing the intake air velocity flowing in the intake
manifold.
* * * * *